In an automotive powertrain, fast and smooth transitions of the driveline's backlash region following a torque increase request can be challenging because of uncertainties in operational parameters such as input torque, driveline friction and the size of the backlash, just to name a few. These uncertainties vary from vehicle to vehicle and even within the same vehicle as it ages. As a result, it may be difficult to determine when the driveline is in the backlash region and when the backlash region has been traversed. One system for detecting a lash zone is described in U.S. Pat. No. 9,037,329, issued on 19 May 2015 and entitled Lash Zone Detection in a Hybrid Electric Vehicle, which is hereby incorporated herein by reference.
Other systems and methods may be employed for determining backlash, but in at least some of these, the adjustments that are made to the driveline torque to control the backlash may result in a lowering of the pre-lash requested torque to decrease the rate that the driveline passes through backlash. This decrease in backlash transition rate combined with the uncertainties described above may lead to an unacceptably slow tip-in response to achieve a smooth backlash transition. It would therefore be desirable to have a system and method for controlling backlash in a vehicle powertrain that overcomes at least some of these issues.